1. Field of Invention
The present invention relates to method of image compression, and particularly relates to image compression method by applying an intelligent output buffer input and output control determining the starting location of storing the compressed pixels in a larger buffer.
2. Description of Related Art
Compression has key benefits in cost reduction of storage device and speedup in accessing the compressed data. Most popular still image compression standards including JPEG, JPEG2000 are lossy algorithms which cause data difference by quite high degree of difference between the compressed-decompressed image and the original image during the procedure of image compression. The data loss caused by lossy compression algorithm degrades the image quality which might not be acceptable in some applications.
There are very few lossless image compression algorithms of image data reduction. One of the most commonly adopted approach is taking differential value between adjacent pixels and applying the so called “entropy coding” or “Variable Length Coding” method which uses the shortest code to represent the most frequent happened pattern which does not guaranty the data ratio due to the uncertainty of the complexity of the image to be compressed.
Lossy compression algorithms can achieve higher compression rate, for example, the JPEG has between 10 to 20 times compression ratio, at the cost of sacrificing the image quality and large amount of computing power and temporary storage buffer. Sharp image quality can be achieved by the lossless compression algorithm but the compression rate is most likely lower than that of the popular lossy algorithms like JPEG or JPEG2000.
The method of this invention of image data compression is to achieve a reasonable high compression ratio with simple means of realizing in both hardware and software without sacrificing much the image quality compared to prior art lossless compression algorithms and has an input-output buffer control which more accurately determines the starting location of each group of compressed pixels with high speed of compression and decompression.